Many semiconductor manufacturing processes, for example the formation of contacts, etch through one or more layers of oxide material disposed in the vicinity of a nitride material. For example, in the formation of a contact, a field oxide layer must be etched down to the nitride layer at the bottom of a feature to subsequently form a metal contact. However, during this etching process the nitride layer formed over the gate structures of the contact may also be etched and become significantly reduced in thickness, leading to electrical shortage and performance degradation in the completed device.
Accordingly, the inventors have provided improved methods of selective etching of materials on a substrate.